Finger lever for a valve drive of an internal combustion piston engine

ABSTRACT

A finger lever (1) is made as a sheet metal part without chip removal and, seen in transverse cross-section, it has a U-shaped profile opening downwards. An upper crosswall of this finger lever (1) comprises an opening (10) of essentially rectangular shape as viewed from above, a roller (3) which can be contacted by a cam (6) being arranged in the opening (10). Side walls (8 and 9) which extend downwards from the crosswall (7) receive a pin (5) which serves to mount the roller (3). Upper edges (11 and 12) of the side walls (8 and 9) have a convex shape. The rigidity of such a finger lever (1) is increased by the fact that the vertical extent of the side walls is increased to such an extent that the roller (3) is situated entirely within this vertical extent of the side walls (8 and 9).

FIELD OF THE INVENTION

The invention concerns a finger lever made as a sheet metal part withoutchip removal for a valve drive of an internal combustion piston engine,the finger lever, as seen in cross-section, having a U-shaped profileformed by an upper crosswall facing a cam and comprising, in a centralregion of the finger lever, an opening of essentially rectangular shapeas seen in a top view, said opening receiving a roller which is inrolling contact with the periphery of the cam, the U-shaped profilebeing further formed by side walls which extend downwards from thecrosswall and receive a pin with the roller mounted for rotationthereon, while edges of the side walls which delimit the opening have aconvex shape.

BACKGROUND OF THE INVENTION

Rocker arms for the valve drive of internal combustion piston engineswere generally made in the past as castings and provided with a rollermounted on a rolling bearing to reduce friction at the point of contactof the cam on the rocker arm. This structure has also been used inmaking finger levers out of sheet metal by cold forming without chipremoval. However, problems have been encountered in such sheet metalfinger levers which are relatively thin-walled, and therefore lighterand more economical than cast finger levers, because it was not possibleto design them with an adequate rigidity.

A cold-formed finger lever of the generic type described above is knownfrom DE-A 39 29 486. To rigidify this sheet metal finger lever, outwardsprojecting ribs are arranged on the side walls below the location of thepin. It has been determined on the one hand that these ribs do notstiffen the finger lever sufficiently and, on the other hand, said ribsincrease the width of the finger lever. But since, precisely inmulti-valve cylinder units only a small space is available for thefinger levers arranged next to each other, the finger levers cannot beprovided with such ribs.

OBJECTS OF THE INVENTION

It is an object of the invention to rigidify a finger lever made ofsheet metal without chip removal without influencing the width of thefinger lever.

SUMMARY OF THE INVENTION

The invention achieves this object by modifying the vertical extent ofthe side walls to make them so large that the roller is situated withinthis extent of the side walls. Thus the rigidity of the finger lever canbe increased by enlarging the side walls in the direction of the cam.All the other dimensions of the finger lever remain unchanged so thatthis structural modification does not influence the rest of the designdimensions of the finger lever.

According to a further development of the invention, a radius of theconvex edges corresponds to a radius of the roller. Thus the side walls,the apex of whose convex edges is situated in the region of a planepassing through a central longitudinal axis of the pin, end with theradius of the roller. However, it is also possible to lengthen the sidewalls to such an extent that a distance is obtained between said edgesand the periphery of the roller situated at a lower level. In this case,the cam would have to penetrate into the rectangular opening.

According to still another feature of the invention, the surfaces of theedges adjacent to the two end faces of the roller comprise recesses.These recesses reliably prevent the cam which actuates the finger leverfrom coming into contact with the side walls of the finger lever due toslight axial displacements of the finger lever. A further advantage ofthese recesses is that splash oil can collect in them and be transferredto the end faces of the roller and thus into the rolling bearing.

As an alternative to the recesses in the side walls of the aboveembodiment, it is also possible to configure the side walls in a Z-shapein vertical direction in the region of the opening above the pinlocation. A Z-shaped configuration means that starting from theirvertical extent, the side walls are at first bent into a horizontalportion and then again into a vertical portion. Due to the Z-shaped sidewalls, a diminishing of cross-section which would occur with the use ofrecesses is prevented. Although the Z-shape of the side walls results inthe formation of ribs on their outer surfaces, these ribs do not presentthe disadvangtages of the ribs of the prior art provided at the loweredge of the finger lever. It must be taken into account, namely, thatthe outer surfaces of the side walls are curved in the region of theupper edges so that there is no risk, even in the case of thisdeformation, of having to arrange adjoining finger levers at greaterdistances to each other due to the ribs in the upper region of the sidewalls.

It is further possible to configure the recesses so that the radius attheir base is larger than the radius of the edges. This gives therecesses the shape of a sickle. The same ratios can be applied to theedges of the side walls having a Z-shaped configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a finger lever of the invention,

FIG. 2 is a longitudinal cross-section through the finger lever of FIG.1,

FIG. 3 is a sectional view along line III--III of FIG. 2, and

FIG. 4 is a sectional view of a further embodiment of a finger levershowing the region of a roller arranged therein.

DETAILED DESCRIPTION OF THE DRAWINGS

A finger lever referenced at 1 in FIG. 1 can be supported at one endregion 2 on a lifter post, not represented. The finger lever receives aroller 3 in a central region and acts in a second end region 4 on an endof a valve stem of a gas exchange valve, not shown. The roller 3 isrotatably mounted on a pin 5 in the finger lever 1 and contacted by acam 6 of a camshaft. The finger lever as a whole is U-shaped, that is tosay, the U-shaped profile in this preferred embodiment is open at itsend away from the cam 6. It is, however, also possible to use a fingerlever having a profile open in the direction of the cam 6 as shown, forexample, in U.S. Pat. No. 4,796,483. The measures of rigidificationwhich will now be described can be equally well used in a structure of afinger lever of this type.

In the cross-section of FIG. 2, which shows the finger lever 1 withoutthe roller 3, it can be seen that the finger lever 1 comprises an uppercrosswall 7 and side walls 8, 9 which are shown with more details inFIG. 3. In the central region of the finger lever 1, the crosswall 7comprises a rectangular opening 10. The side walls 8 and 9 compriseedges 11 and 12 having a convex shape, and the roller 3 is mounted onthe pin 5 in corresponding bores 13 and 14 of the side walls, a needleroller bearing, not shown, being disposed between the pin 5 and theroller 3.

As can already be seen in FIG. 1, the roller 3 is situated within thevertical extent of the side walls 8 and 9. This results in anadvantageous rigidification of the finger lever. In the region of theedges 11 and 12, however, the side walls are deformed parallel to eachother to a certain extent in outward direction so that, on the whole, aZ-shaped profile is obtained. This results in the formation of recesses15 and 16 in the surfaces of the edges 11 and 12 facing the ends of theroller 3. As can be seen in FIG. 2, a radius R₁ at the edges 11 and 12is smaller than a radius R₂ at the base of the recesses. Thus therecesses 15 and 16 are sickle-shaped as viewed in longitudinalcross-section. These recesses prevent the cam from coming into contactwith the side walls 8 or 9 in case of an axial play in the mounting ofthe camshaft or in a guide of the finger lever.

In a further embodiment of the invention shown in FIG. 4, side walls 17and 18 comprise recesses 19 and 20 which are formed in these side walls19 and 20 by chipless stamping. These recesses 19 and 20 have the samefunction as the recesses of FIG. 3 made by the Z-shaped deformation ofthe finger lever.

I claim:
 1. A finger lever (1) made as a sheet metal part without chipremoval for a valve drive of an internal combustion piston engine, thefinger lever (1), as seen in cross-section, having a U-shaped profileformed by an upper crosswall (7) facing a cam (6) and comprising, in acentral region of the finger lever (1), an opening (10) of essentiallyrectangular shape as seen in a top view, said opening (10) receiving aroller (3) which is in rolling contact with the periphery of the cam(6), the U-shaped profile being further formed by side walls (8, 9, 17,18) which extend downwards from the crosswall (7) and receive a pin (5)with the roller (3) mounted for rotation thereon, while edges (11, 12)of the side walls (8, 9, 17, 18) which delimit the opening (10) have aconvex shape, characterized in that the roller (3) is arranged entirelywithin the vertical extent of the side walls (8, 9, 17, 18).
 2. A fingerlever according to claim 1 made as a sheet metal part without chipremoval, characterized in that a radius (R₁) of the convex edges (11,12) corresponds to a radius of the roller (3).
 3. A finger leveraccording to claim 1 made as a sheet metal part without chip removal,characterized in that recesses (15, 16, 19, 20) are provided in surfacesof the side walls (8, 9, 17, 18) which are adjacent to the edges (11,12) and situated opposite the two end faces of the roller (3).
 4. Afinger lever according to claim 1 made as a sheet metal part withoutchip removal, characterized in that, in the region of the opening (10)above the pin arrangement, the side walls (8, 9) extend vertically in aZ-shape.
 5. A finger lever according to claim 3 made as a sheet metalpart without chip removal, characterized in that a radius (R₁) of theedges (11, 12) is smaller than a radius (R₂) at the base of the recesses(15, 16).